When you think of evolution, you no doubt imagine a process that takes millions of years to produce any notable results. In other words, evolution doesn’t happen overnight.

Or does it?

While the most significant evolutionary changes do take millions of years to happen – the creation of new species or the appearance of new body parts, for example – evolution can also be observed on a much shorter timescale, and often within a person’s lifespan.

Think for a moment about domestication, a process through which human-induced selection has resulted in significant modifications to plants and animals.

These are examples of evolution in response to selective forces, and they are happening before our eyes.

Evolution in real-time can also be observed under the scrutiny of the scientific method, and researchers call it “experimental evolution”.

How it works

The basics are quite simple:

1) Choose a species of plant or animal to study
2) Split the species into several groups
3) Apply an external pressure to one or more groups
4) See how the affected groups “evolve” over a period of time

For example, you could split a population of weed into several groups, apply a weed-killer to half of those groups and compare the treated and untreated individuals at the end of the experiment.

Only weeds that have shown resistance to the weed-killer will be able to leave descendants (because you can’t leave descendants if you are dead). These descendants will inherit the weed-killer resistance and will pass it on to subsequent generations.

The result? Resistance to the weed-killer is “selected” in the treated groups, just as it would be in nature. In this sense, we’ve created our own miniature version of evolution without having to wait millions of years for a result.

But the really interesting questions follow: what is the genetic basis for the evolution of resistance adaptations?

Are there trade-offs between resistance and other fitness-related traits? Are there limits to the evolution of resistance? Can evolution be reversed if we use ancestral conditions?

Experimental evolution enables us to answer such questions.

Microbes

Professor Richard Lenski from Michigan State University and his collaborators are among the most prominent researchers currently showing evolution in action.

Their trick is to study organisms amenable to a life in the lab and with short generation times. And if it’s short generation times you are after, where better to look than microbes.

Lenski’s started his experiment way back in 1988 with 12 populations of the commonly occurring Escherichia coli (E.coli) bacterium. That study is still ongoing – more than 22 years and 52,000 generations of bacteria later – and continues to show evolutionary changes in response to selection and randomness.

Among the jewels produced by Lenski’s long-term study is the emergence of E.coli families that exploit their environment in ways that reduce competition for resources.

In particular, Lenski and his team found that one of the 12 E. coli families evolved the ability to use a compound known as “citrate” as a food source. By evolving this ability, this family was able to breed more successfully and survive longer than the other families.

Another exceptional finding of Lenski’s lab, recently published in Science, indicates that the ability of organisms to evolve (evolvability) can itself evolve.

This remarkable discovery was achieved by freezing bacteria at some points early in the selection experiment and reviving them years later to assay the outcome of competition between groups of bacteria whose descendants either eventually prevailed or were extinct at a later time.

In the words of Richard Lenski “Imagine Neanderthals brought back to live among us. How would they fare at chess or football?”

Put this in the context of the microbial world and the achievements by Lenski’s group and you will get a glimpse of the power of experimental evolution in helping us to understand nature.